Which expression can be simplified to find the slope of the trend line in the scatterplot? On a graph, a line goes through points (4, 21) and (8, 35). StartFraction 21 minus 35 Over 8 minus 4 EndFraction StartFraction 8 minus 4 Over 21 minus 35 EndFraction StartFraction 35 minus 21 Over 8 minus 4 EndFraction StartFraction 8 minus 4 Over 35 minus 21 EndFraction